What are the treatment guidelines for Community-Acquired Pneumonia (CAP)?

Community-Acquired Pneumonia Treatment Guidelines

Outpatient Treatment (Non-Hospitalized Patients)

For healthy adults without comorbidities, amoxicillin 1 g three times daily is the preferred first-line antibiotic, with doxycycline 100 mg twice daily as an acceptable alternative. 1

• Macrolides (azithromycin 500 mg day 1, then 250 mg daily; or clarithromycin 500 mg twice daily) should only be used in areas where pneumococcal macrolide resistance is less than 25%. 1
• For patients with comorbidities (diabetes, heart disease, COPD, chronic kidney disease, immunosuppression), combination therapy is required: β-lactam (amoxicillin-clavulanate, cefpodoxime, or cefuroxime) plus either a macrolide or doxycycline. 1
• Alternatively, respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily, moxifloxacin 400 mg daily, or gemifloxacin 320 mg daily) is appropriate for patients with comorbidities. 1

Inpatient Treatment (Non-ICU Hospitalized Patients)

For hospitalized patients not requiring ICU admission, use either β-lactam plus macrolide combination therapy OR respiratory fluoroquinolone monotherapy—both regimens have strong evidence and equivalent efficacy. 1

Preferred Regimens (Equal Efficacy):

• Option 1: Ceftriaxone 1-2 g IV daily plus azithromycin 500 mg IV/PO daily 1
• Option 2: Levofloxacin 750 mg IV/PO daily OR moxifloxacin 400 mg IV/PO daily as monotherapy 1

Alternative Regimen:

• β-lactam (ceftriaxone, cefotaxime, or ampicillin-sulbactam) plus doxycycline 100 mg twice daily (conditional recommendation, lower quality evidence) 1

Penicillin-Allergic Patients:

• Use respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) 1

Critical Timing Consideration:

• Administer the first antibiotic dose while still in the emergency department—delayed administration beyond 8 hours increases 30-day mortality by 20-30%. 2, 1

Severe CAP Requiring ICU Admission

All ICU patients with severe CAP require mandatory combination therapy with a β-lactam plus either azithromycin OR a respiratory fluoroquinolone. 1

Standard ICU Regimen:

• β-lactam (ceftriaxone 2 g IV daily, cefotaxime 1-2 g IV every 8 hours, or ampicillin-sulbactam 3 g IV every 6 hours) PLUS either:
  • Azithromycin 500 mg IV daily, OR
  • Levofloxacin 750 mg IV daily, OR
  • Moxifloxacin 400 mg IV daily 2, 1

Penicillin-Allergic ICU Patients:

• Respiratory fluoroquinolone (levofloxacin 750 mg IV daily) plus aztreonam 2 g IV every 8 hours 1

Coverage for Drug-Resistant Pathogens

Pseudomonas aeruginosa Risk Factors:

Add antipseudomonal coverage if the patient has: structural lung disease (bronchiectasis), recent hospitalization with IV antibiotics within 90 days, or prior respiratory isolation of P. aeruginosa. 2, 1

• Regimen: Antipseudomonal β-lactam (piperacillin-tazobactam 4.5 g IV every 6 hours, cefepime 2 g IV every 8 hours, imipenem 500 mg IV every 6 hours, or meropenem 1 g IV every 8 hours) PLUS either:
  • Ciprofloxacin 400 mg IV every 8 hours OR levofloxacin 750 mg IV daily, OR
  • Aminoglycoside (gentamicin or tobramycin 5-7 mg/kg IV daily) plus azithromycin 2, 1

Community-Acquired MRSA Risk Factors:

Add MRSA coverage if the patient has: post-influenza pneumonia, cavitary infiltrates on imaging, prior MRSA infection/colonization, or recent hospitalization with IV antibiotics. 2, 1

• Regimen: Add vancomycin 15 mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) OR linezolid 600 mg IV every 12 hours to the base regimen 2, 1

Duration of Antibiotic Therapy

Treat for a minimum of 5 days and until the patient is afebrile for 48-72 hours with no more than one sign of clinical instability. 2, 1

Clinical Stability Criteria (Must Meet ALL):

• Temperature ≤37.8°C (100°F)
• Heart rate ≤100 beats/min
• Respiratory rate ≤24 breaths/min
• Systolic blood pressure ≥90 mmHg
• Oxygen saturation ≥90% on room air
• Able to take oral medications
• Normal mental status 2

Extended Duration Required For:

• Legionella pneumophila: 14-21 days 1
• Staphylococcus aureus: 14-21 days 1
• Gram-negative enteric bacilli: 14-21 days 1
• Extrapulmonary complications (meningitis, endocarditis): individualized, typically >14 days 2

Transition from IV to Oral Therapy

Switch to oral antibiotics when the patient is hemodynamically stable, clinically improving, able to ingest medications, and has normal gastrointestinal function—typically by day 2-3 of hospitalization. 2, 1

• Patients do not need to remain hospitalized solely to receive oral antibiotics; discharge as soon as clinically stable with no other active medical problems. 2
• Oral step-down options: amoxicillin 1 g three times daily plus azithromycin 500 mg daily, or continue the same fluoroquinolone orally. 1

Diagnostic Testing Recommendations

Obtain blood cultures and sputum cultures (if productive cough) before initiating antibiotics in all hospitalized patients. 1

Expanded Testing Indicated For:

• All ICU admissions 1
• Patients empirically treated for MRSA or P. aeruginosa 1
• Failure to respond to initial therapy within 48-72 hours 2
• Severe CAP with septic shock 2

Follow-Up and Monitoring

• Chest radiograph is not required before hospital discharge in patients with satisfactory clinical recovery. 2
• Clinical review at 6 weeks is recommended for all patients, with chest radiograph reserved for those with persistent symptoms, physical signs, or high risk for underlying malignancy (smokers, age >50 years). 2
• For hospitalized patients, evaluate clinical response at 48-72 hours; if no improvement, obtain repeat chest radiograph, inflammatory markers, and additional microbiological specimens. 1

Critical Pitfalls to Avoid

• Never use macrolide monotherapy in hospitalized patients—this provides inadequate coverage for typical bacterial pathogens like S. pneumoniae. 1
• Avoid macrolide monotherapy in any setting where local pneumococcal macrolide resistance exceeds 25%—this significantly increases treatment failure risk. 1
• Do not use cefuroxime, cefepime, piperacillin-tazobactam, or carbapenems as first-line empiric therapy unless specific risk factors for P. aeruginosa or MRSA are present—these broader agents are associated with increased resistance and C. difficile risk. 1
• Do not delay antibiotic administration beyond 8 hours in hospitalized patients—this substantially increases mortality. 1
• Avoid extending therapy beyond 7 days in responding patients without specific indications—this increases antibiotic resistance without improving outcomes. 1